Hydrogenated block copolymer, elastomer composition comprising hydrogenated block copolymer, seal member comprising elastomer composition, plug body and medical plug

Abstract

A hydrogenated block copolymer (P) obtained by hydrogenation of a coupled polymer represented by (A-B)n-X, wherein the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) is 10 mass % to 40 mass %, the peak top molecular weight of a diblock component corresponding to (A-B) in (A-B)n-X is 160,000 to 225,000, the proportion of a dibranched component corresponding to a case in which n is 2 in (A-B)n-X is 10 mass % to 30 mass % based on the total hydrogenated block copolymer (P), the proportion of a tribranched component corresponding to a case in which n is 3 in (A-B)n-X is 40 mass % to 70 mass % based on the total hydrogenated block copolymer (P), and the ratio of the tribranched component to the dibranched component M (mass of tribranched component/mass of dibranched component) is 2 or more.

1 . A hydrogenated block copolymer (P) obtained by hydrogenation of a coupled polymer represented by the following formula (1):
   (A-B) n -X  (1)
   wherein A represents a polymer block comprising a vinyl aromatic monomer unit as a main component, B represents a polymer block comprising a conjugated diene monomer unit as a main component, n is an integer of 1 or greater, and X represents a residue of a coupling agent or a residue of a polymerization initiator, wherein
 a content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) is 10 mass % to 40 mass %, 
 a peak top molecular weight of a diblock component corresponding to (A-B) in the formula (1) is 160,000 to 225,000, 
 a proportion of a dibranched component corresponding to a case in which n is 2 in the formula (1) is 10 mass % to 30 mass % based on the total hydrogenated block copolymer (P), 
 a proportion of a tribranched component corresponding to a case in which n is 3 in the formula (1) is 40 mass % to 70 mass % based on the total hydrogenated block copolymer (P), and 
 a ratio M (mass of tribranched component/mass of dibranched component) of the tribranched component to the dibranched component is 2 or more. 
   
     
     
         2 . The hydrogenated block copolymer according to  claim 1 , wherein the proportion of the diblock component is 10 mass % to 40 mass % based on the total hydrogenated block copolymer (P). 
     
     
         3 . The hydrogenated block copolymer according to  claim 1 , wherein a proportion of a tetra- or higher-branched component corresponding to a case in which n is an integer of 4 or more in the formula (1) is 10 mass % or less based on the total hydrogenated block copolymer (P). 
     
     
         4 . The hydrogenated block copolymer according to  claim 1 , wherein a weight average molecular weight of the total hydrogenated block copolymer (P) is 350,000 to 500,000. 
     
     
         5 . The hydrogenated block copolymer according to  claim 1 , wherein a proportion of a 1,2-bond and a 3,4-bond in the conjugated diene monomer unit in the hydrogenated block copolymer (P) is 50 mol % to 80 mol %. 
     
     
         6 . The hydrogenated block copolymer according to  claim 1 , wherein a degree of hydrogenation of the conjugated diene monomer unit in the hydrogenated block copolymer (P) is 80 mol % or more. 
     
     
         7 . An elastomer composition comprising the hydrogenated block copolymer according to  claim 1 . 
     
     
         8 . The elastomer composition according to  claim 7 , comprising 10 to 50 parts by mass of a polypropylene resin and 30 to 200 parts by mass of a non-aromatic softener based on 100 parts by mass of the hydrogenated block copolymer. 
     
     
         9 . The elastomer composition according to  claim 7 , wherein, when an elastomer composition sheet produced under the following conditions is cut into a 10 cm×10 cm square and both the surfaces are observed with a microscope, the number of grains having a diameter of 200 m or more calculated by the following expression is 0;
 [Production of Elastomer Composition Sheet]
 a sheet material comprising the hydrogenated block copolymer is melt-kneaded with a twin screw extruder at a setting temperature of 230° C., and the obtained kneaded product is molded using a T die at a number of revolutions of the screws of 300 rpm to produce an elastomer composition sheet having a thickness of 500 m; 
 
 [Calculation Expression for Number of Grains]
   Number of grains=[total number of grains having a diameter of 200 μm or more observed]×Y/X
 
 
 wherein X represents a weight of the composition sheet (g), Y represents an amount of the hydrogenated block copolymer in the composition sheet (g), and a calculated value rounded off to the nearest whole number is employed as the number of the grains. 
 
     
     
         10 . The elastomer composition according to  claim 7 , comprising no polyphenylene ether resin. 
     
     
         11 . The elastomer composition according to  claim 7 , comprising no surface-treated silica. 
     
     
         12 . The elastomer composition according to  claim 7 , comprising no polyphenylene ether resin and surface-treated silica. 
     
     
         13 . A seal member comprising the elastomer composition according to  claim 7 . 
     
     
         14 . A plug body comprising the elastomer composition according to  claim 7 . 
     
     
         15 . A medical plug for use in a medical application, comprising the elastomer composition according to  claim 7 . 
     
     
         16 . The hydrogenated block copolymer according to  claim 2 , wherein a proportion of a tetra- or higher-branched component corresponding to a case in which n is an integer of 4 or more in the formula (1) is 10 mass % or less based on the total hydrogenated block copolymer (P). 
     
     
         17 . The hydrogenated block copolymer according to  claim 2 , wherein a weight average molecular weight of the total hydrogenated block copolymer (P) is 350,000 to 500,000. 
     
     
         18 . The hydrogenated block copolymer according to  claim 3 , wherein a weight average molecular weight of the total hydrogenated block copolymer (P) is 350,000 to 500,000. 
     
     
         19 . The hydrogenated block copolymer according to  claim 16 , wherein a weight average molecular weight of the total hydrogenated block copolymer (P) is 350,000 to 500,000. 
     
     
         20 . The hydrogenated block copolymer according to  claim 2 , wherein a proportion of a 1,2-bond and a 3,4-bond in the conjugated diene monomer unit in the hydrogenated block copolymer (P) is 50 mol % to 80 mol %.